Flexible metal wall and method of making same



Patented Apr. 24, 1928.

* UNITEDSTATES" g 3 PATENT. 'oFFicE.

FRED K. isnzznminnenn, or CLEVELAND nmen'rsronio, assienon, BY MESNE as-j SIGNMENTS, To run FULTON SYLPHON. COMPANY, 01? xnoxvnmn, mnnnnssnn,

A CORPORATION OEDELAWARE, pp

FLEXIBLE METAL WALL Ann METHOD OF MAKING SAME.

No Drawing. Application filed truly 26,

The present =invention, relating, as indicated, toflexible metal wallsand methodsof making. the same, is particularly directed to an improved method of making tubular corrugated flexible metal walls, which are com monly called bellows, of a metal which may be worked and formed in a softcondition and then tempered after the completion of the forming operations as distinguished from the methods which are .now"in:.use;f*all50f which involve the tempering of the metal during the forming operations'and either the subsequent removal of the temper, or the removal of thetemper at one or more'stages during the forming process. To the accomplishment of theforegoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out-in the claims. J a a The following description sets forthindetail one methodandone product exemplifying my invention, such disclosed procedure and product constituting, however, but one of various applications ofthe principles of my invention.

Metallic bellows, such as arenow generally used in thermostats, valves and similar articles are commonly made by one of two methods. In one method a tube is first drawn and is then successively corrugated by pressing the metal outward and inward from the original tube wall and then rolling these initially formedcorrugations to deepen and narrow the same until the desired shape is finally produced. In this method it is necessary to anneal the partially formed bellows one or more times in the forming operations, since the pressing of the metaloutwardly and inwardly sets up a considerable temper, particularly at the crests of the inner and outer corrugations, and unless this temper is reduced or removed. the metal becomes extremely stiff and is very liable to breakage at this point in a. subsequent operation. Brass is almost invariably employed in the processnamed, and brass is tempered by 'being rolled, stretched or otherwise worked, the amount of temper being directly proportional to the amount of deformation of the metal so that practically any desired temper may be given a bellows when completed by varying the number of rolling operations and 1924. Serial No. 7 28,375.

the amountof deformation given to the metal subsequent to. the last annealing operation.

' TllBwCliiQf disadvantagesot' this method,

which isthe one in common use, are, first, that only a.relat1vely soft metal, such as .brass, is ordinarily employed because of the difliculty of rolling iron, steel, nickel or similar metals, and second,,the numberofseparate operations which are required, there be ing operations and usually one or more annealing operations. .Another disadvantage is that the resultingbellows is not strong since it is formed of a relativelyxweak metal,

namely, brass, and cannot be employed where high pressures are necessary unless either the thickness. of the wall ismade'sufliciently great,;whichi in most cases is not practicable because the bellowsis. then stifi'and uni-e sponsive in movement,ior by using a two or ent method is a development of the fluid pressure method referred to above. I first draw a tube of either relatively pure iron, whichmay contain a small percentage of carbon, say 10%, or of somealloy of iron from'which carbon is entirely absent. I After being drawn, and if necessary at one or more stages of the several drawing operations, I anneal this tube so that when completely drawn it is in a soft or unten'ipered condition. This soft tube is then expanded by fluid pressure introduced within it into spaced corrugations. as gin the manner described in my Patent No. 1,506.966. granted Sept. 2, 1924, and. this expansion of the tube into a bellows may be accomplished either in one i mg usually not less than-five separate rollknown that pure iron may be converted into steel or carbonized in this manner and that the carbon will penetrate a distance of about Q of an inchinto the iron exposed to the carbon-carrying gas. As the ordinary bellows .isbut atew thousandths of airinch, usually tro n .005 to .012 the penetration is entirely sutlicient to convert all of the metal of the bellows into steel.

The bellows may also be tempered by packing with a carbonaceous material, such as charcoal or any of the ordinary case hardiening compounds, and after the cementa-tion process, as this operation is ordinarily termeth the bellows should be cooled in the ,i'urnaceand then reheated to a temperature above the critical temperature of the metal, after which it should he quencl'ied either in oil or water for the purpose oi. refining; the coarse structurewhich has resulted Irom the rtubonizirurtreatment. In. case carbon to the amount of aboutfi tainedat about 1580 F3, after which the metal is're-heated to about 750'F.. in order to dra and temper, and relieve the strain which has been set up By thus'inducing the desiredproperties in the metal after the formation of the bellows, thatwis, by converting iron. into steel after the bellows has first been formed, I am able to use an inexpensive material and to give it. an extremely high elasticity and tensile strength in the finished article. Thus. the metal of a steel bellows made by this meth'odv'will have a tensile strength of about 125,000 pounds per squareinch. while that of an ordinary brass bellows, as now made has a tensile strength of not to exceed (55,-

000 pounds, and-are thus unfitted for many desirable'uses for which my improvedJbeh lows is entirely adequate. my new method to use amatjerial into which the desired properties ofelasticity and high tensile strength may be induced after the final formation of the article,, and so far as I now knowf this limits the material ft has been induced 1n the metal the temperature should bemam It is essential in.

which may be used to pure iron or to iron alloys which can be converted into steel alloys in the manner described: after the bellows has been completely formed.

It will be understood that while I preier to 'l'orm the iron bellows by fluid pressure because of the econon'iyof that'process and the quality of the product, it may be formed mechanically and in either case given thesubsequent treatment described to convert the metal to steel.

'Various' alloys of iron may be similarly treated for the purpose of inducing qualities into the finished bellows. Thus an alloy of iron with about 3 to 5' per cent nickel lends itselhreadilyto the carbonizing and. subsequent treatments and produces a steel hav ing markedly better qualitiesthan those to be found in a pure steel such as has been discussed.above." I 7 Other forms may be employed. embodying the features of my invention instead of the one here explained, change being made in the form or construction,provided the elements stated-by any of the following "claims or. the equivalent of such stated elements be employed, Whether produced by my preferred" method or by others embodyingstcps equivalent to those stated in the following claims. a 1

a I thereforeparticularly point out and dis tinctly claim as my invention:

1. In a method of making flexible deeply corrugated tubular metal walls, the steps whichconsistin forming. a tube ofsoft ductile metal into a deeply'corrugated tube, and, then alloying. with the metal of said tube a substance capable oi? increasing the elastic limit: and tensile strength thereof;

2 Ina method of makinga deeply corrugatedrsteetbellows, the stepswhich consist] in forming an iron tube into a. deeply corrugated tube, and then convert-ingthe metal:

of such tube into steel. 7 Signed by me, this 23rd day of July, 1924.

FRED l K. BEZZENBERGER 

